1240728521 has 2 divisors, whose sum is σ = 1240728522. Its totient is φ = 1240728520.

The previous prime is 1240728499. The next prime is 1240728539. The reversal of 1240728521 is 1258270421.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1173816121 + 66912400 = 34261^2 + 8180^2 .

It is a cyclic number.

It is not a de Polignac number, because 1240728521 - 2⁶ = 1240728457 is a prime.

It is not a weakly prime, because it can be changed into another prime (1240728121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 620364260 + 620364261.

It is an arithmetic number, because the mean of its divisors is an integer number (620364261).

Almost surely, 2^1240728521 is an apocalyptic number.

It is an amenable number.

1240728521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1240728521 is an equidigital number, since it uses as much as digits as its factorization.

1240728521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8960, while the sum is 32.

The square root of 1240728521 is about 35223.9765074871. The cubic root of 1240728521 is about 1074.5474268730.

Adding to 1240728521 its reverse (1258270421), we get a palindrome (2498998942).

The spelling of 1240728521 in words is "one billion, two hundred forty million, seven hundred twenty-eight thousand, five hundred twenty-one".